The present invention relates to mechanical engineering and, more particularly, it relates to a method of packing long-sized porous bodies such as locked-coil steel ropes or stacked bands used as traction members, for example, in hydraulic cylinders with a flexible piston rod.
This invention can be used most advantageously for packing long-sized porous bodies operating in a fluid medium between zones of different pressure, for example, in hydropneumatic cylinders with rods in the form of long-sized porous bodies such as ropes which may be employed in hoisting devices, in feed systems of mining machines, in various cranes, in feed means of drilling tools, in power rigging for moving mine headframes and other buildings and structures.
The present invention can also be used for the sealing and protection of long-sized porous bodies subjected to the effect of seawater, mine water and atmosphere and to other corrosion effects.
A problem exists in the tightness of seal and corrosion resistance of long-sized porous bodies operating in zones with different pressure. Such bodies may include the rods of hydraulic and pneumatic cylinders, especially, flexible rods in the form of ropes. Conventional cable compound based on thickened petroleum oils filling the interwire space of ropes is, under the effect of pressure difference between zones of different pressure, squeezed out to the zone of lower pressure, comes out to the rope surface and is removed therefrom.
Fluid medium rushes to the thus formed voids, laying down passages in the interwire space for coming out to the zone of lower pressure while bypassing the sealing members designed to seal the outer surface of the rope. This causes a loss of seal by hydraulic cylinders with flexible rods, a reduction of working pressure and traction force of the hydraulic cylinder, as well as inconsiderable leakage of the fluid medium used as the working fluid in the hydraulic cylinder and lost irreparably in the space surrounding the cylinder.
In hoisting facilities, for example, the discharge of cable compound from the inner interwire space of the rope to the outside and the formation of interwire voids filled with corrosive medium is observed when the rope passes round a snatch pulley changing the rope direction in space, during which passage there is changed both the relative position of individual wires and of rope layers relative each other.
This is conducive to intensive corrosion of rope wires and premture failure of the rope.
In order to preclude the afore-described phenomena, it is expedient that the pores of a long-sized porous body, especially of a body such as rope, be filled with a packing substance capable of withstanding the violation of its uniformity under the effect of mechanical and hydraulic loads.
There is known a method of greasing a steel rope (cf., PCT Application No. 82/01201, Int. Cl. D 07 B 7/12// B 05 C 3/12), which comprises drawing the rope through a chamber filled with lubricant under pressure. Use is made of a fluid lubricant, preferably, machine oil, supplied to the chamber by a pump at discharge pressure. The rate of drawing the steel rope through the chamber is selected such that the spaces in the rope should absorb the oil but that there should be no efflux of oil.
However, the use of oils as packing substance does not enable one to attain internal tightness of a long-sized porous body in the form of a rope due to low resistance of fluid lubricants to shear stresses occurring during operation of ropes in supports between rope layers and individual wires under the effect of pressure difference between zones with different pressures and of rope bending loads. This results in a flow of grease in the interwire space, its extrusion outside of the rope, penetration of the working fluid inside the rope and gradual loss of seal by the higher-pressure zone filled with working fluid whose composition differs from that of the packing grease.
There is known a method of external coating of a rope by drawing it through a chamber filled with a pressurized compound of uncured rubber, with subsequent curing of the rubber (cf., U.S. Pat. No. 4,057,956, class D 07 B 1/16, published Nov. 15, 1977).
Said latter prior art method only permits of coating with a packing layer of cured rubber the pores on the external surface of a long-sized porous body and fails to ensure the filling with the packing of inner pores, i.e., interwire space of the rope, because of insufficient plasticity of the packing material.
Moreover, the rubber compound is characterized by low thixotropic properties ensuring a rapid restoration of broken bonds between particles of substance and of the substance structure, which leads to the loss of uniformity of packing material when it is forced through pores of different shapes. Therefore, when a long-sized porous body with an outer rubber coating is used as a flexible rod of pneumohydraulic cylinders passing round a snatch pulley, considerable unit pressures in the zone of contact between the flexible rod and pulley cause gradual deterioration of the external coating and the communication of the surrounding fluid medium via thus formed ruptures with inner pore voids. Further, when a portion with deteriorated coating emerges in the higher-pressure zone, pressurized working fluid penetrating the long-sized porous body and seeking to leave said body via internal passages in the lower-pressure zone affects the rubber coating from the inside. The coating starts acting as a rubber hose communicated with the higher-pressure zone, however, since it is not protected by external reinforcing members, the coating is only capable of providing a seal against low internal pressure; otherwise, the coating will deteriorate and the long-sized porous body will lose its seal. In addition, the external coating of ropes is subject to mechanical effect of relatively moving wires of the upper layer which add to the deformation of the coating.
All this will affect the reliability of seal of long-sized porous bodies packed by the prior art method.
It is especially important to ensure a reliable seal of porous bodies such as ropes used as flexible rods of hydraulic cylinders, which may be employed advantageously to provide for an adequately long stroke of the piston with the hydraulic cylinder developing considerable forces.
Known in the art is a power cylinder with a flexible piston rod (cf., U.S.S.R. Inventor's Certificate No. 1,048,113, Int. Cl. E 21 C 5/06), comprising a cylinder with a piston, front and rear covers to each of which there are attached packing assemblies of the flexible rod fashioned as traction rope. The packing assembly is made in the form of a sleeve mounted for rotation in the cylinder body and accommodating thereinside a stack of packing elements. The cylinder utilizes compressed air as the working medium. In so doing, the operation of the cylinder involves considerable losses of the working medium due to a rapid wear of the stack of packing elements upon repeated passage of the flexible rod therethrough. The loss of the working medium is further caused by the fact that the stack of packing elements made of an elastic material does not provide for a tight fit of the inner surface relative to the flexible rod because the diameter of the latter varies in the course of operation under different loads. In addition, the loss of the working medium occurs through the interwire space in the rope cross-section. The loss of working medium causes a considerable reduction in the power and efficiency of the power cylinder.
There is also known a prior art power cylinder with a resilient packing element of the rope (cf., U.S.S.R. Inventor's Certificate No. 446.646, Int. Cl. E 21 C 5/06 // F 16 j 15/56), comprising a resilient element, a gland packing encompassing the rope and a pressure member interacting with the gland packing and feed cylinder cover through the intermediary of a threaded joint, the pressure member being made in the form of coaxially arranged tapered sleeves one of which is split while the other one interacts with the cylinder cover and split sleeve through the intermediary of resilient element.
The operation of said prior art cylinder is accompanied by a decrease in the amount of packing in the chamber (due to its carryover by the rope). The loss of density of packing caused by its carryover by the rope is compensated for by the resilient element pressing against the packing.
Under elevated pressures, however, there occurs a loss of the working medium both through the gland packing because of its fibrous structure and through the rope section via interwire space, which prevents the power cylinder from developing great forces.
Further known in the art is a power cylinder (cf., U.S.S.R. Inventor's Certificate No. 1,040,262, Int. Cl. F 16 L 1/04) comprising a piston placed in a cylindrical body and having a flexible traction rod (rope) passed through an axial opening in a cover attached to the cylindrical body, said cover provided with a packing in the form of a chamber filled with a viscous material and communicated with a froth generator coupled hydraulically to a pressure source and mounted on the apparatus outside of the end cover thereof. In the case of considerable loss of working medium through the packing chamber, the latter is supplied with a foaming agent increasing the viscosity of the material and causing an increase of the hydraulic resistance of fluid in the packing chamber.
The fact that the packing is based on increasing the viscosity of the fluid present in the packing chamber and raising, as a result, its hydraulic resistance does not rule out the leakage of fluid. This leakage is directly proportional to the pressure inside the packing chamber and to the rate of travel of the traction rod (rope). In addition, the leakage occurs through the rope body via interstices between the rope wires. Said leakage is so high as to prohibit the use of such packing in hydraulic cylinders with high working pressure and with high frequency of reciprocation of the piston with flexible rod.